The dominoes are falling. A major U.S. gun retailer refuses to sell assault-style rifles and high-capacity magazines, and stops selling guns to kids under 21. The biggest chain store in the U.S. follows suit on age limits. Banks, airlines, insurers and rental car companies rush to cancel special discount programs for members of the National Rifle Association, perceiving the brand to be toxic.

They’re small victories. But after years of legislative sclerosis, they signify an important shift in momentum.

In the fraught weeks since the mass shooting at Marjory Stoneman Douglas high school, perception of the NRA’s stranglehold over U.S. gun policy has shifted dramatically. Student protesters are challenging corporations to end their affiliation with the NRA and manufacturers of assault weapons, often with surprising success.

After the shooting, and in the presence of grieving survivors, the Republican-controlled Florida Senate and House of Representatives both rejected bans on assault weapons such as the AR-15 that ripped through Stoneman Douglas. (Instead, absurdly, a state appropriations committee wants to spend $67 million to train teachers as armed marshals.)

Since 2007, at least 173 people have been killed in mass shootings involving AR-15s across the U.S., according to a New York Times analysis.

The NRA continues to frame civilian access to weapons of mass slaughter as an issue of “freedom.” In its arsenal of influence, direct campaign contributions are the thin edge of the wedge. Its insidious Second Amendment “report cards” dole out the highest ratings to candidates whose voting records support the most unfettered access to guns, while the alarmist NRATV channel streams over multiple platforms.

But the Parkland survivors, versed in statistics and raw with emotion, have momentum on their side. Corporations have been shedding their NRA affiliations like snakeskin, while those choosing to maintain special NRA programs have served to keep the protest narrative alive.

The evidence of the Twitter campaigns’ success will not be found in share prices or quarterly reports, but in tarnished brands.

The goal of these grassroots campaigns is not simply to encourage consumers to spend their money elsewhere. Their real impact is in deflating the NRA’s influence by demonstrating how easily reputations can be tainted by association.

The lobby group will lose its power over candidates if its endorsement is perceived as a stain on their character. A pithy tweet by student Sarah Chadwick sums it up nicely: “We should change the names of AR-15s to ‘Marco Rubio’ because they are so easy to buy.”

The most successful grassroots campaigns go beyond consumer behaviour to connect with a broader narrative of social reform. The Montgomery bus boycott was not carried to success on the economic clout of its riders — three-quarters of whom were African Americans — but the resonance of their message.

Champions of socially progressive issues tend to be at an electoral disadvantage; they’re generally younger and vote less than their conservative counterparts. But youth and diversity are strengths when it comes to wielding economic clout.

As Jeet Heer has argued in the New Republic, progressives largely occupy our most valued target demographics. The marketplace is where their leverage exists.

Perhaps there is no better indicator of which way the wind is blowing than President Trump’s eagerness to seize the narrative as his own. This week, in a bipartisan meeting on school safety, he accused fellow Republicans of being “afraid” of the NRA. “They have great power over you people,” he said in front of the cameras. “They have less power over me.”